1870.] The Surveys of India. 455 



In the year 1829 a trigonometrical survey in the Bombay Pre- 

 sidency was commenced by Lieutenant Shortrede, on an indepen- 

 dent base and point of departure. This survey proceeded in an 

 unsystematic manner until it was brought under Colonel Everest's 

 control in 1831, when, finding that no use could be made of this 

 confused net of triangulation, the Colonel directed that the longitu- 

 dinal series should be taken up where he left off in 1823. This 

 was concluded in 1841, the series extending over a distance 315 

 miles in length. 



The space at our disposal will not admit of a detailed account 

 of the several series of triangulation carried out by the Trigono- 

 metrical Survey Department ; they will, however, be seen by refer- 

 ence to the accompanying map. Besides the great arc series, 

 extending from Cape Comorin to Dehra Dhoon, there are two 

 longitudinal series, the one extending from Cachar, in Assam, to 

 Peshawur, and the other from Calcutta to Kurrachee: between 

 these are numerous series of triangles, those to the east of the great 

 arc being at distances of about one degree, or 60 miles apart, taking 

 meridional directions, thus forming what is called a gridiron system, 

 similar to that adopted in the French and Kussian surveys. Base 

 lines are measured at the extremities of the longitudinal chains, and 

 at the points where the chains cross Colonel Everest's arc; thus 

 the triangulation is divisible into large quadrilateral figures, with a 

 base line at each corner. 



Colonel Everest was succeeded in the appointment of Superin- 

 tendent of the Great Trigonometrical Survey and Surveyor-General 

 of India by Captain (afterwards Sir) Andrew Waugh, in December, 

 1843, who held the combined offices for seventeen years. Sir 

 Andrew Waugh left the service in 1861, when he was succeeded 

 by Colonel J. T. Walker, K.E., as Superintendent of the Great 

 Trigonometrical Survey, and by Colonel Thuillier, E.A., as Sur- 

 veyor-General of India, both which officers respectively fill those 

 appointments at the present time. 



The charts of the trigonometrical operations are zincographed 

 on a scale of 4 miles to the inch, and the geodetical co-ordinates for 

 each station with azimuths and linear distances are entered upon 

 them, so that each chart forms a brief but complete record of the 

 survey results. Skeleton charts of levels, on a scale of 2 miles to 

 the inch, are also prepared and photozincographed ; these show 

 the combined results of both trigonometrical and spirit levelling 

 reduced to the common datum of the mean sea-level of Kurrachee 

 harbour. 



Revenue Survey. — The Kevenue Survey Branch, in the Bengal 

 Presidency, first commenced in the year 1822. It comprises a scien- 

 tific periphery admeasurement of the land by means of angular and 

 linear measurements, performed with theodolites and steel chains ; 



